Change the name of _snapshot_at attr to _snapshot_elapsed_time
Change the name of _snapshot_at attr to _snapshot_elapsed_time

ktnyt/chainer,niboshi/chainer,kiyukuta/chainer,okuta/chainer,wkentaro/chainer,ktnyt/chainer,ronekko/chainer,aonotas/chainer,chainer/chainer,jnishi/chainer,wkentaro/chainer,cupy/cupy,jnishi/chainer,niboshi/chainer,okuta/chainer,chainer/chainer,hvy/chainer,jnishi/chainer,wkentaro/chainer,okuta/chainer,wkentaro/chainer,keisuke-umezawa/chainer,jnishi/chainer,hvy/chainer,okuta/chainer,niboshi/chainer,ktnyt/chainer,chainer/chainer,hvy/chainer,cupy/cupy,chainer/chainer,keisuke-umezawa/chainer,delta2323/chainer,kashif/chainer,niboshi/chainer,keisuke-umezawa/chainer,cupy/cupy,rezoo/chainer,ysekky/chainer,hvy/chainer,anaruse/chainer,tkerola/chainer,ktnyt/chainer,keisuke-umezawa/chainer,cupy/cupy,pfnet/chainer